OPACITY OF BLACK SMOKE - CALCULATED VARIATION WITH PARTICLE-SIZE AND REFRACTIVE-INDEX

The opacity of a black smoke (an aerosol of carbon spheres) is calculated from the Mie theory for several log-normal particle distributions.Calculations are presented at a wavelength of 0.55 μm for particle geometric mean diameters in the 10−3–1-μm range and geometric mean standard deviations in the 0 (monodisperse) to 0.4 range.For-a given mass concentration the extinction coefficient and, therefore, the opacity can vary by a factor of 2 or more as the size distribution is varied.For absorptive indexes (m2) near 0.7, typical of carbon, the smoke opacity is only weakly dependent on the real part of the particle refractive index.© 1979 Optical Society of America.